CN102414607B - Liquid crystal display device and method for manufacturing transparent electrode - Google Patents

Abstract

The present invention provides a liquid crystal display device that can suppress light leakage from the periphery of non-selected pixels without reducing the pixel aperture ratio, thereby improving contrast. The liquid crystal display device 1 includes the following structure: first and second transparent substrates 5a and 5b facing each other with a predetermined gap; a liquid crystal layer 8 disposed between the opposing surfaces of the first and second transparent substrates 5a and 5b; a first stripe-shaped transparent electrode 3a formed on the surface of the first transparent substrate 5a facing the second transparent substrate 5b in a stripe-like shape; a transparent resin film 22 formed by forming a stripe-shaped black film 21 perpendicular to the first stripe-shaped transparent electrode 3a on the surface of the second transparent substrate 5b facing the first transparent substrate 5a; and an inverted trapezoidal recess 22a on the film surface corresponding to the position between the black film 21; and a second stripe-shaped transparent electrode 30b formed in an inverted trapezoidal shape in the recess 22a of the resin film 22.

Description

Liquid crystal display device and method for manufacturing transparent electrode

technical field

The present invention relates to a liquid crystal display device having a simple matrix electrode structure and a method for manufacturing a transparent electrode.

Background technique

2 is a cross-sectional view showing a vertical alignment type liquid crystal display device as an example of a liquid crystal display device having a simple matrix electrode structure. The vertical alignment type liquid crystal display device 1 includes a liquid crystal panel 2 and displays an image using the liquid crystal panel 2 .

In the liquid crystal panel 2, a first strip-shaped transparent electrode 3a made of ITO (indium tin oxide) or the like is formed on one side of a first transparent substrate 5a made of a glass plate or the like. A first alignment film 4a is formed on the strip-shaped transparent electrode 3a, and an alignment rubbing process is applied to the first alignment film 4a. A second strip-shaped transparent electrode 3b made of ITO or the like is formed on the surface, a second alignment film 4b is formed on the second strip-shaped transparent electrode 3b, and an alignment rubbing process is performed on the second alignment film 4b, so The first transparent substrate 5a and the second transparent substrate 5b, for example, use polymer balls 6 or the like as spacers, so that the first alignment film 4a and the second alignment film 4b are bonded together in a direction facing each other, and then The panel main body 2a is formed by sealing the periphery with a frame-shaped packing 7 . In the case of this liquid crystal panel 2, the first transparent substrate 5a on the lower side is used as the rear substrate 5a on the backlight (light source) side, and the second transparent substrate 5b on the upper side is used as the front substrate 5b on the display side. Transmissive LCD panel.

In addition, liquid crystal layer 8 is formed by sealing liquid crystal in the space (cell gap) between first transparent substrate 5 a and second transparent substrate 5 b by vacuum injection method, dropping method, or the like. In the case of this liquid crystal panel 2, a nematic liquid crystal (negative type liquid crystal) having a negative dielectric constant anisotropy is used as a liquid crystal, whereby a vertical alignment type liquid crystal is formed.

Furthermore, a first polarizer 9a is attached on the plate surface of the first transparent substrate 5a opposite to the side contacting the liquid crystal layer 8, and on the opposite side of the second transparent substrate 5b contacting the liquid crystal layer 8. A second polarizer 9b is pasted on the panel to complete the liquid crystal panel.

3 is a diagram showing an electrode structure for simple matrix driving of a vertical alignment type liquid crystal display device. Among the first and second strip-shaped transparent electrodes 3a and 3b, for example, a plurality of first strip-shaped transparent electrodes 3a on the lower side are formed in parallel in the lateral direction (horizontal direction), and are formed in a horizontal stripe pattern as a whole. The scanning electrodes connected to the scanning side driving circuit 10, the second strip-shaped transparent electrodes 3b on the upper side are formed in parallel in the longitudinal direction (vertical direction), and are formed in a vertical stripe pattern as a whole, and serve as a connection with the signal side driving circuit. The signal electrodes connected to 11 form a simple matrix electrode structure through these first and second strip-shaped transparent electrodes 3a and 3b. In the liquid crystal panel 2, the intersection of the first and second strip-shaped transparent electrodes 3a and 3b formed parallel to each other in the horizontal and vertical directions in this way serves as one pixel. In other words, the liquid crystal panel 2 arranges the pixels into a grid, and configures the horizontal and vertical first and second strip-shaped transparent electrodes 3a and 3a for the pixels arranged in the grid, and selects the required horizontal and vertical first electrodes 3a and 3a. And the second strip-shaped transparent electrodes 3a and 3a to apply voltage. Thereby, the liquid crystal in the liquid crystal layer (liquid crystal cell) 8 of the pixel located at the intersection of the first and second strip-shaped transparent electrodes 3a and 3b selected in the horizontal and vertical directions is driven. That is, the liquid crystal panel 2 is a liquid crystal panel having a simple matrix electrode structure and performing simple matrix driving (duty driving). However, when the number of display pixels is large, the driving becomes time-sharing multiplex driving.

FIG. 4 is a diagram showing an arrangement structure of polarizing plates in a vertical alignment type liquid crystal display device. Of the first and second polarizers 9a and 9b, the first polarizer 9a has an absorption axis in the direction indicated by an arrow 9a', and the second polarizer 9b has an absorption axis in the direction indicated by an arrow 9b'. That is, the first polarizer 9a and the second polarizer 9b are arranged such that the respective absorption axes 9a' and 9b' are vertical (crossed nicol arrangement), and the display mode of the liquid crystal panel 2 becomes normally black (Normally Black). black).

Fig. 5 is a diagram for explaining driving of a vertical alignment type liquid crystal display device, (a) is a diagram in a non-driven state, and (b) is a diagram in a driven state. The liquid crystal panel 2 is in the non-driven state where no voltage is applied between the first and the second strip-shaped transparent electrodes 3a and 3b, as shown in FIG. 5(a), the first and the second strip-shaped transparent electrodes 3a and 3b The liquid crystal molecule 8a in the liquid crystal layer (liquid crystal cell) 8 between is by the effect of the first and the second alignment film 4a and 4b, makes the long-axis direction of the molecule be aligned to be perpendicular to the first and the second transparent substrate 5a and 5b. The optical axes are substantially aligned, but the major axes of the molecules are aligned with a slight tilt angle (pre tilt) in order to control the alignment direction, etc., and the polarization state of light passing through the liquid crystal layer 8 hardly changes. Thus, the light (linearly polarized light) transmitted through the first polarizing plate 9a on the backlight side of the liquid crystal panel 2 enters the second polarizing plate 9b on the display surface side of the liquid crystal panel 2 almost unchanged, and The polarizer 9b is almost blocked or absorbed, resulting in a dark display (black display).

On the other hand, in the drive state where a voltage is applied between the first and second strip-shaped transparent electrodes 3a and 3b, as shown in FIG. 5(b), the first and second strip-shaped transparent electrodes 3a and 3b The liquid crystal molecules 8a in the liquid crystal layer 8 between them are aligned in a direction approximately perpendicular to the electric field due to the negative dielectric constant anisotropy, that is, they are aligned approximately parallel to the first and second transparent substrates 5a and 5b, so that the liquid crystal molecules 8a passing through The polarization state of light in the liquid crystal layer 8 changes. Thus, the light passing through the first polarizer 9a on the backlight side of the liquid crystal panel 2 changes its polarization state and exits from the liquid crystal layer 8, so that the light of the second polarizer 9b on the display surface side of the liquid crystal panel 2 is aligned with the absorption axis 9a. 'The polarization component perpendicular to the transmission axis increases, resulting in a bright display (white display).

Here, applying a direct current to the liquid crystal is harmful, and if the direct current is continuously applied to the liquid crystal, the liquid crystal material will deteriorate. In addition, the used nematic liquid crystal (negative type liquid crystal) having negative dielectric constant anisotropy also produces alignment disorder at a relatively low voltage below a predetermined voltage, so the pixel is leaked to the signal of the adjacent pixel. Driven by current etc. (called crosstalk), the contrast is deteriorated. Accordingly, in driving the vertical alignment type liquid crystal display device 1 , the applied signal is inverted at a constant cycle in order to eliminate the DC component. In addition, in order to prevent crosstalk, a predetermined off voltage equal to or lower than a critical voltage (threshold) for driving liquid crystals is applied to non-selected pixels.

In this way, the vertical alignment liquid crystal display device 1 has: first and second transparent substrates 5a and 5b facing each other with a predetermined interval; a first strip-shaped transparent electrode 3a and a second strip-shaped transparent electrode 3b. The strip-shaped transparent electrodes 3a are arranged in parallel on the surface of the first transparent substrate 5a opposite to the second transparent substrate 5b, and the second strip-shaped transparent electrodes 3b are arranged in parallel in the direction perpendicular to the first strip-shaped transparent electrodes 3a. On the surface of the second transparent substrate 5b opposite to the first transparent substrate 5a; the liquid crystal layer 8 is disposed between the respective opposite surfaces of the first and second transparent substrates 5a and 5b, and is composed of a negative medium. Electrical constant anisotropy, the orientation of liquid crystal molecules 8a is substantially perpendicular to the first and second transparent substrates 5a and 5b, if a predetermined threshold voltage or more is applied between the first and second strip-shaped transparent electrodes 3a and 3b voltage, the orientation of the liquid crystal molecules 8a becomes approximately parallel to the first and second transparent substrates 5a and 5b; the first polarizer 9a and the second polarizer 9b, the first polarizer 9a is configured on the first transparent substrate 5a has an absorption axis 9a' in a predetermined direction on the surface opposite to the surface opposite to the second transparent substrate 5b, and the second polarizer 9b is arranged on the second transparent substrate 5b opposite to the first transparent substrate 5a. The surface on the opposite side of the opposing surface has an absorption axis 9b' perpendicular to the absorption axis 9a' of the first polarizer 9a, and the vertical alignment type liquid crystal display device 1 performs simple matrix driving (duty driving).

6 is a schematic cross-sectional view omitting the structure of an alignment film, a spacer, a sealant, a liquid crystal layer, a polarizing plate, etc. of a vertical alignment liquid crystal display device, (a) showing conventional first and second strip-shaped transparent electrodes (b) is a diagram showing an electric field generated by an off-state voltage applied between the conventional first and second transparent electrodes of (a). Generally, the first and second strip-shaped transparent electrodes 3a and 3b used in such a vertical alignment type liquid crystal display device 1 are shown in FIG. The opposing surfaces of the second transparent substrates 5a and 5b are tapered, and the entire electrode is trapezoidal with the opposing surfaces of the first and second belt-shaped transparent substrates 5a and 5b as bases.

In such trapezoidal first and second strip-shaped transparent electrodes 3a and 3b, as shown by arrows of solid lines in FIG. The electric field generated by the off-state voltage between the first and second strip-shaped transparent electrodes 3a and 3b in the pixel (central part of the pixel) is neatly approximately parallel to the first and second transparent substrates 5a and 3b. 5b vertical direction, but the ends (pixel periphery) of the first and second strip-shaped transparent electrodes 3a and 3b in the pixel are not neatly substantially parallel to the direction perpendicular to the first and second transparent substrates 5a and 5b. direction, and become an oblique electric field, the oblique electric field makes the orientation of the liquid crystal molecules 8a in the non-selected pixels disordered, so as shown by the hollow arrows in FIG. , so that the off-state transmittance becomes higher, resulting in a decrease in contrast.

In order to solve this problem, for example, as described in Patent Document 1, the following technology is known: a black film (black film) is provided on a portion of the second strip-shaped transparent substrate on the surface opposite to the first transparent substrate without the second transparent electrode. mask), using the black film to cover the tapered end of the second transparent electrode to prevent light leakage at the periphery of the non-selected pixels and improve the contrast.

prior art literature

patent documents

Patent Document 1: Japanese Patent Application Laid-Open No. 5-2161

Contents of the invention

The problem to be solved by the invention

However, in the prior art described above, since the tapered end portion of the second transparent electrode is covered with a black film, there is a corresponding problem that the area contributing to the display of the pixel becomes smaller, that is, the aperture ratio of the pixel becomes smaller. becomes smaller and the display becomes darker.

An object of the present invention is to provide a liquid crystal display device and a method of manufacturing a transparent electrode that can suppress light leakage from the periphery of non-selected pixels and improve contrast without reducing the aperture ratio of pixels.

means of solving problems

In order to achieve the above object, the liquid crystal display device of the present invention is characterized in that it comprises:

first and second transparent substrates 5a and 5b, the first and second transparent substrates 5a and 5b face each other and have a predetermined interval;

a liquid crystal layer 8 disposed between the respective opposing surfaces of the first and second transparent substrates 5a and 5b;

The first strip-shaped transparent electrode 3a is formed on the surface of the first transparent substrate 5a opposite to the second transparent substrate 5b, and is in the shape of stripes;

A transparent resin film 22 formed in a stripe shape along a direction perpendicular to the first strip-shaped transparent electrode 3 a on the surface of the second transparent substrate 5 b facing the first transparent substrate 5 a. A transparent resin film formed after the black film 21, the transparent resin film 22 has an inverted trapezoidal concave portion 22a on the film surface corresponding to the position between the black films 21;

The second strip-shaped transparent electrode 30b, which is in an inverted trapezoidal shape, is formed in the concave portion 22a of the resin film 22 .

In addition, the manufacturing method of the transparent electrode of the present invention is used to manufacture the second strip-shaped transparent electrode 30b in the above-mentioned liquid crystal display device of the present invention, and is characterized in that,

On the surface of the second transparent substrate 5b opposite to the first transparent substrate 5a, a stripe-shaped black film 21 is formed along a direction perpendicular to the first strip-shaped transparent electrode 3a, and then coated by overcoating. (over coat) transparent resin to form a transparent resin film 22 with an inverted trapezoidal concave portion 22a on the film surface corresponding to the position between the black films 21, and form the first transparent resin film 22 in the concave portion 22a of the resin film 22. Two strip-shaped transparent electrodes 30b, thus obtaining an inverted trapezoidal second strip-shaped transparent electrode 30b.

Invention effect

According to the manufacturing method of the liquid crystal display device and the transparent electrode of the present invention, it is possible to provide the following liquid crystal display device and the manufacturing method of the transparent electrode: by forming the existing trapezoidal second strip-shaped transparent electrode into an inverted trapezoidal shape, the An oblique electric field is generated at the periphery of the non-selected pixels, thereby suppressing the disorder of the alignment of the liquid crystal molecules in the non-selected pixels due to the oblique electric field, and disposing a black film on the back side between the second strip-shaped transparent electrodes to realize As a result, the inverted trapezoidal shape of the second strip-shaped transparent electrode can more reliably suppress light leakage from the peripheral portion of the non-selected pixel by the inverted trapezoidal second strip-shaped transparent electrode and the black film without reducing the aperture ratio of the pixel. , which can improve the contrast.

Description of drawings

1 is a schematic cross-sectional view showing a liquid crystal display device having a simple matrix electrode structure of the present invention, (a) is a schematic cross-section showing the shapes of the first and second strip-shaped transparent electrodes, and (b) is a schematic cross-sectional view showing the shape of the first and second strip-shaped transparent electrodes. a) A schematic cross-sectional view of an electric field generated by an off-state voltage applied between the first and second transparent electrodes.

2 is a cross-sectional view of a vertical alignment type liquid crystal display device as an example of a liquid crystal display device having a simple matrix electrode structure.

FIG. 3 is a diagram showing a simple matrix electrode structure of the vertical alignment type liquid crystal display device shown in FIG. 2 .

FIG. 4 is a diagram showing an arrangement structure of polarizing plates in the vertical alignment type liquid crystal display device of FIG. 2 .

FIG. 5 is a diagram for explaining driving of the vertical alignment type liquid crystal display device of FIG. 2 , wherein (a) is a diagram in a non-driven state, and (b) is a diagram in a driven state.

6 is a schematic cross-sectional view of the vertical alignment type liquid crystal display device of FIG. 2 , (a) is a schematic cross-section showing the shape of the conventional first and second strip-shaped transparent electrodes, and (b) is a schematic cross-sectional view showing the shape of the first and second strip-shaped transparent electrodes obtained from (a). A diagram of the electric field generated by the off-state voltage applied between the conventional first and second transparent electrodes.

Detailed ways

Next, an embodiment of the present invention will be described with reference to FIG. 1 . 1 is a schematic cross-sectional view showing a liquid crystal display device having a simple matrix electrode structure of the present invention, (a) is a schematic cross-section showing the shapes of the first and second strip-shaped transparent electrodes, and (b) is a schematic cross-sectional view showing the shape of the first and second strip-shaped transparent electrodes. a) A schematic cross-sectional view of an electric field generated by an off-state voltage applied between the first and second transparent electrodes. In addition, the display device shown in FIG. 1 is characterized in the structure of the second transparent electrode and its manufacturing method, and the structure other than that is the same as that of the vertical alignment type liquid crystal display device shown in FIG. 4 , so for the same structure Parts are given the same reference numerals and detailed explanations are omitted. In addition, in FIG. 1, structures, such as alignment film 4a, 4b, spacer 6, sealing material 7, liquid crystal layer 8, polarizing plate 9a, 9b, etc. are abbreviate|omitted similarly to FIG.

As shown in FIG. 1(a), a transparent resin film 22 is provided on the surface of the second transparent substrate 5b facing the first transparent substrate 5a in the vertical alignment type display device 20 of the present embodiment. The film 22 is a transparent resin film formed after the striped black film 21 is formed in a direction perpendicular to the first strip-shaped transparent electrode 3a, and has an inverted film surface on the film surface corresponding to the position between the black films 21. The second strip-shaped transparent electrode 30 b is formed in the concave portion 22 a of the resin film 22 in the trapezoidal concave portion 22 a. The electrode end portion of the second strip-shaped transparent electrode 30b is formed along the end shape (inverted taper shape) of the concave portion 22a. Different, become an inverted trapezoid. In addition, the second strip-shaped transparent electrode 30b is parallel to the direction perpendicular to the first strip-shaped transparent electrode 3a on the surface (film surface of the resin film 22) of the second transparent substrate 5b facing the first transparent substrate 5a. Since there are a plurality of them, the whole is formed in a striped pattern.

In addition, the second alignment film 4b is formed on the film surface of the resin film 22 planarized by filling the concave portion 22a with the second strip-shaped transparent electrode 30b.

If an example of the manufacturing method of the inverted trapezoidal second strip-shaped transparent electrode 30b is described, firstly, as a first step, on the plate surface of one side of the second transparent substrate 5b, along the first strip-shaped transparent electrode 30b, A stripe-like black film 21 is formed in a direction perpendicular to the electrode 3a. The black mask 21 is, for example, coated with a photosensitive black mask material with a predetermined thickness on the entire surface of one side of the second transparent substrate 5b, and then formed into a predetermined shape (striped pattern) by photolithography.

Next, as a second step, a transparent resin (paint) is coated with a predetermined thickness on the surface of the second transparent substrate 5b facing the first transparent substrate 5a to form a layer corresponding to the position between the black masks 21. A transparent resin film 22 having an inverted trapezoidal concave portion 22a on the film surface. Here, as a target, the thickness ratio of the black film 21 and the resin film 22 for forming the concave portion 22 a is 1:2 to 1:5, and the depth of the concave portion 22 a is 0.1 to 0.5 μm.

Finally, as a third process, the second strip-shaped transparent electrodes 30 b are formed in the concave portions 22 a located on the film surface of the resin film 22 . The second strip-shaped transparent electrode 30b is formed on the entire film surface of the resin film 22 by vapor deposition or sputtering, and then formed into a predetermined shape (striped pattern) by photolithography.

Thereby, as mentioned above, the electrode end portion surrounded by the dotted line of the second strip-shaped transparent electrode 30b is formed along the end shape (reverse taper shape) of the concave portion 22a. As a result, the second strip-shaped transparent electrode 30b is different from the conventional The trapezoidal second strip-shaped transparent electrode 3b is different from the trapezoidal shape, which is formed in an inverted trapezoidal shape. In addition, the second strip-shaped transparent electrode 30b is parallel to the direction perpendicular to the first strip-shaped transparent electrode 3a on the surface (film surface of the resin film 22) of the second transparent substrate 5b facing the first transparent substrate 5a. Since there are a plurality of them, the whole is formed in a striped pattern.

In this way, in the vertical alignment type display device 20 of the present embodiment, the existing trapezoidal second strip-shaped electrodes 3a are formed into inverted trapezoids, so that the liquid crystal layer 8 of the second strip-shaped transparent electrodes 30b is The side surface is all arranged in the plane parallel with the first and second transparent substrate 5a and 5b from its one end to the other end, so that the off-state voltage applied between the first and second strip-shaped transparent electrodes 3a and 30b The generated electric field, as shown by the arrow of the solid line in (b) of FIG. Pixel peripheral portions) are all neatly substantially parallel to the direction perpendicular to the first and second transparent substrates 5a and 5b.

Therefore, it is possible to provide a liquid crystal display device and a method of manufacturing a transparent electrode that can suppress the generation of an oblique electric field at the peripheral portion of an unselected pixel, suppress the disorder of the orientation of the liquid crystal molecules 8a in the unselected pixel due to the oblique electric field, and The black film 21 is arranged between the back sides of the second strip-shaped transparent electrodes 30b and the second strip-shaped transparent electrodes 30b are formed into an inverted trapezoid. Both the strip-shaped transparent electrode 30b and the black film 31 can more reliably suppress the light leakage from the periphery of the non-selected pixels, so as to improve the contrast.

In addition, in the vertical alignment type display device 20 of the present embodiment, although the black film, the resin film, and the second transparent electrode having an inverted trapezoidal shape are formed on the front substrate side of the display surface side, they may also be formed on the rear substrate side of the backlight side. In addition, it can also be formed on both the front substrate and the rear substrate on the side of the display surface. The present invention is not limited to this embodiment, and various modifications can be made within a range not departing from the gist.

The reference signs are explained as follows:

1Vertical alignment type liquid crystal display device

3a The first strip-shaped transparent electrode

30b second strip-shaped transparent electrode

5a first transparent substrate

5b second transparent substrate

8 liquid crystal layer

21 black film

22 resin film

22a recessed part

Claims (2)

1. Liquid crystal display device, is characterized in that, comprises: first and second transparent substrates, the first and second transparent substrates face each other and have a predetermined interval; a liquid crystal layer disposed between opposing surfaces of the first and second transparent substrates; A first strip-shaped transparent electrode, which is formed on the surface of the first transparent substrate opposite to the second transparent substrate, and is in the shape of stripes; A transparent resin film formed after forming a stripe-shaped black film on the surface of the second transparent substrate opposite to the first transparent substrate along a direction perpendicular to the first strip-shaped transparent electrode A transparent resin film formed, the transparent resin film has an inverted trapezoidal recess on the film surface corresponding to the position between the black films; a second strip-shaped transparent electrode, which is in an inverted trapezoidal shape, formed in the concave portion of the resin film, The opening of the inverted trapezoidal recess faces the first strip-shaped transparent electrode, In the extending direction of the first strip-shaped transparent electrode, the width of the opening of the inverted trapezoidal recess is greater than the width of the bottom of the inverted trapezoidal recess. 2. A method for manufacturing a transparent electrode, used to manufacture the second strip-shaped transparent electrode in the liquid crystal display device described in claim 1, characterized in that, On the surface of the second transparent substrate opposite to the first transparent substrate, a stripe-shaped black film is formed along a direction perpendicular to the first strip-shaped transparent electrode, and then coated with a transparent resin , to form a transparent resin film having an inverted trapezoidal concave portion on the corresponding surface of the position between the black film, and form a second strip-shaped transparent electrode in the concave portion of the resin film, thereby obtaining an inverted trapezoidal The second strip-shaped transparent electrode.